A Magnetic Resonance Imaging apparatus (hereinafter, an “MRI apparatus”, as necessary) detects Nuclear Magnetic Resonance signals (hereinafter, “NMR signals”, as necessary) emitted from atoms (e.g., hydrogen atoms) in an examined subject (hereinafter, a “patient”) by using a coil. Further, the MRI apparatus converts the detected NMR signals into raw data called ‘k-space data’ and to obtain an image (hereinafter, an “MR image”, as necessary) indicating a distribution of target atoms by performing a reconstructing process that applies a conversion to the k-space data. By applying an inverse Fourier transform to the k-space data, the MRI apparatus obtains the MR image corresponding to the signals detected by the coil.
The k-space data are obtained by taking images of a three-dimensional target object. The MRI apparatus repeatedly takes one-dimensional images to obtain a two-dimensional cross-sectional image or a three-dimensional volume image during an imaging sequence. The MRI apparatus performs the one-dimensional image taking process by using a method called a frequency encoding process. To perform image taking processes in other dimensions, the MRI apparatus repeatedly performs the image taking process while changing the phase by using a method called a phase encoding process. To obtain a two-dimensional cross-sectional image, the MRI apparatus selects a cross section serving as an image taking target, by performing a slice selecting process on the three-dimensional target object.
In this situation, for example, to acquire k-space data corresponding to a desired resolution “256×256” in a k-space, the MRI apparatus sets the number of k-space lines to be imaged by performing the phase encoding process to “256” and repeatedly performs a one-dimensional image taking process 256 times. Thus, the image taking process takes a long period of time. For this reason, a parallel imaging technique has been studied as a method for reducing the number of k-space lines imaged by performing the phase encoding process. The parallel imaging technique is a technique developed by focusing on the fact that, when the k-space data are acquired by using a plurality of coils simultaneously, the sensitivity level varies depending on the positional arrangement of the coil. Examples of the parallel imaging technique include a SENSE-based (sensitivity encoding) technique and a SMASH-based (simultaneous acquisition of spatial harmonics) technique (e.g., a GRAPPA (generalized autocalibrating partially parallel acquisition) method). The parallel imaging technique has been applied to many MRI apparatuses and is widely used.